1. Field of the Invention
The present invention relates to an object movement simulation apparatus in which works, such as assembling of parts or components, confirming behavior of movable parts of an apparatus, are implemented by a simulation, such works being involved in a problem of collision (interference) between object-to-object.
2. Description of the Related Art
Recently, there are increased occasions in which a three-dimensional CAD system is used for a product design. However, in case of a product which consists of a lot of parts and is complicated in arrangement, an assembling work for assembling the product is also complicated, and thus there is such a fear that it is overlooked that an occurrence of a collision with other parts at the stage of a design disenables even a man of experience to assemble the product, or an occurrence of a collision of movable parts with other parts makes it difficult to perform a desired operation.
According to the conventional CAD system for a mechanism design, it is possible to arrange designed parts at optional positions and in figures as if a product has been apparently assembled. However, in order for confirmation of no overlooking as mentioned above, there is a need to actually manufacture the parts constituting the product or models of the parts by way of trial and to assemble the product.
In view of the foregoing, it is desired that a simulation apparatus, which is capable of performing a simulation as to whether a designed product can be actually assembled or disassembled, or whether a movable part can implement a desired movement without any collision with other parts, without actually manufacturing the product by way of trial, appears.
In order to inspect as to whether assembling and the like are possible through the simulation, generally, there is adopted a technology of searching a disassembling route involved in no occurrence of a collision starting from the state of a product after assembling, on the basis of information as to parts designed with the use of a three-dimensional CAD system (cf. for example, "GEOMETRIC REASONING ABOUT MECHANICAL ASSEMBLY, Randall H. Wilson Jean-Claude Latombe, Stanford University, Artifical Inteligence 71 (2), December 1994", and "AN EFFICIENT SYSTEM FOR GEOMETRIC ASSEMBLY SEQUENCE GENERATION AND EVALUATION, Bruce Romney, Stanford University, Proc. 1995 ASME. Int 1 Computers in Engineering Conf., pp.699-712).
A technology for performing a collision check to check as to whether there is any occurrence of a collision and also to determine collision points involved in an occurrence of the collision is proposed, for example, in Japanese Patent Application Laid Open Gazette Hei. 7-134735, Japanese Patent Application Laid Open Gazette Hei. 8-77210, Japanese Patent Application Laid Open Gazette Hei. 9-27046, "Lecture Papers of 13th Robotics Society of Japan, pp. 373-374", and "Lecture Papers of 51th National Meeting of Information Processing of Japan, pp. 53-54".
It is important for the simulation apparatus as mentioned above, form a viewpoint of being easy to do assembling and disassembling, to know the closest point between an object (part) now on translation and another object (part), as well as an inspection as to whether a collision occurs. Of the above-mentioned technology of collision check, there is a technology in accordance with which the closest point between object-to-object can be determined. The use of such a technology makes it possible to perform a translation (assembling, disassembling, etc.) simulation while confirming the existence of the closest point in such a manner that a virtual object indicative of the closest line coupling closest point-to-closest point, as well as an object (part) of interest of the translation simulation and objects (parts) existing around the object of interest, are disposed in a virtual three-dimensional space, so that a three-dimensional image, which is obtained when the virtual three-dimensional space is looked at from a certain viewpoint, is displayed on a display screen.
FIG. 34 is an explanatory view useful for understanding a movement simulation.
It is assumed that an object A, an object B and an object C are disposed in a virtual three-dimensional space, and the object A is translated along the arrow X.
At that time, at the respective positions (a, b, c, d and e show in FIG. 34) in the mid way of translation of the object A, a virtual object (hereinafter, it happens that the virtual object is referred to as a closest line without distinction between it and the closest line) representative of the closest line MAL coupling two closest points of a first closest point most closed to the object A on an object (in case of positions a-d, the object B; in case of position e, the object C) most closed to the object A, and a second closest point on the object A most closed to the first closest point is kept to display on a display screen always during a translation of the object A. This feature makes it possible to know a "margin" free from a collision of the object A under movement with other objects.
However, if this is simply implemented, it may happen that the closest line MAL disappears in the object.
FIGS. 35(A) and 35(B) and FIGS. 36(A) and 36(B) are typical illustrations each showing the manner in which the closest line disappears in the object. FIGS. 35(A) and 35(B) are concerned with the state before movement. FIGS. 36(A) and 36(B) are concerned with the state after translation. FIG. 35(A) and FIG. 36(A) are plan views. FIG. 35(B) and FIG. 36(B) are front views. It is assumed that the front views shown in FIG. 35(B) and FIG. 36(B) are displayed on a display screen, and the object A is translated along the arrow X shown in FIG. 35(A).
In the state before translation shown in FIGS. 35(A) and 35(B), the closest line MAL is indicated in not only the plan view shown in FIG. 35(A), but also the front view shown in FIG. 35(B). On the other hand, in the state after translation shown in FIGS. 36(A) and 36(B), while the closest line MAL is indicated in the plan view shown in FIG. 36(A), the closest line MAL disappears in FIG. 36(B) displayed on the display screen.
Thus, when the closest line MAL disappears, it is impossible to identify the "margin" free from a collision. Therefore, there is a need that a translation of an object is interrupted, three-dimensional images produced through altering a viewpoint are sequentially displayed to find a three-dimensional image easy to see the closest line, and then a translation of the object is resumed. Particularly, in the event that a large number of parts are assembled, when a closest line MAL is varied while a certain object is translated among a lot of parts, or when a closest line MAL disappears in various objects, there is a need to often repeat an interruption of a translation of an object, an alteration of the viewpoint, and a resumption of the translation. This involves a troublesomeness in operation.
In order to solve such a troublesomeness in operation, it is considered that an object on a three-dimensional image is displayed with a line drawing such as a wire frame, etc. However, in the event that a plurality of objects are overlapped, lines are congested, and as a result it is considered that it would bring about an image which is difficult to intuitively grasp an arrangement relation among objects and a closest-point relation between objects.
The foregoing problems are similar in the matter of a collision point in the event that a collision occurs. Also in this case, it is considered that the collision point disappears in objects, and in the event that an object is displayed with a line drawing, it is considered that it would bring about an image which is difficult to intuitively grasp an arrangement relation among objects and a closest-point relation between objects.